[aprssig] Handling incoming messages for different SSID
Lynn W. Deffenbaugh (Mr)
ldeffenb at homeside.to
Sun Nov 13 16:04:49 CST 2011
On 11/13/2011 4:27 PM, Georg Lukas wrote:
> Should the application notify the user of incoming messages to all their
> SSIDs (DO1GL*)? Only of messages to the configured SSID (DO1GL-5)? Or
> configured SSID and no-SSID (DO1GL-5, DO1GL)?
Yes, but I'm with you, I cannot put my eyes on the actual spec that says
that. I remember reading something about a station should "read" (their
word, not mine) any message for the same callsign as the station but
should only acknowledge messages addressed to the specific -SSID of the
station. Maybe it's Kenwood that set that standard, but I know it's
written down somewhere in the pages and pages of "additional" specs.
> Should there be a difference in display of such messages? Right now, I
> do not display the user's own callsign due its redundancy.
Given that I support various types of user-enabled "eavesdropping" in
APRSISCE/32, I already display the callsign-SSIDs of both ends of a
conversation. This is no different than watching the raw message
packets on the air or via APRS-IS, I just format them nicely. In fact,
I leave it up to the user if they want to receive all of their own
messages (regardless of -SSID), but I default that option to ON.
> I suppose, the application should only send ACKs for messages directed
> at the configured callsign-ssid to avoid duplication problems. Is that
Yes only ack the specific callsign-SSID of your instance. From aprs101.pdf:
> The receiving station will only acknowledge messages addressed to itself,
> and not any messages received which were addressed to any group callsign.
> Note: The receiving station will acknowledge all messages addressed to
> itself, even if it is operating in an Alternate Net (see Chapter 4:
> APRS Data
> in the AX.25 Destination and Source Address Fields).
> Should the application strip the SSID from the destination callsign in
> outgoing messages?
No, any message sent is sent from a specific callsign-SSID to a specific
callsign-SSID. Otherwise, you may never get an ack causing excessive
> Where can I find documentation / specification regarding the above
Read, study, sleep on, and re-read aprs101.pdf. There's lots of
subtleties in there! Like:
> The receiving station will read all messages with the Addressee field
> set to
> ALL, QST or CQ.
So, in addition to "reading" all messages to the base callsign, you're
also supposed to "read" messages to those three additional group names
(and support local user-configurable additional ad-hoc message groups).
Kenwood adds their own (not sure what it is right now) and I also listen
to APRSIS-32 and APRSIS-CE as pre-defined "special" group names in
keeping with the Kenwood example.
Lynn (D) - KJ4ERJ - Author of APRSISCE for Windows Mobile and Win32
More information about the aprssig